An example of a known printing machine is shown in DE-B2-2632455. This known device is designed for the exchanging of such operating parts as an inking unit and a printing cylinder but also a counter-pressure cylinder of a photo- or rotogravure printing machine and comprises a carriage having means for supporting the said parts thereon. After having been run into a position in front of the printing machine, and the front panel thereof has been removed, the wheel-axes of the carriage are turned through 90 degrees by means of a linkage. Thereafter the carriage is as a whole drawn into the housing of the printing machine by means of an endless chain. The whole exchange of the said parts as well as their securing in and loosening from the printing machine, respectively, is done manually. There is not shown or disclosed any means to securely hold the cylinders on the carriage.